The present invention generally concerns machine-vision, particularly systems and methods for lighting/illuminating objects in machine-vision systems.
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings hereto: Copyright (copyright) 1998-2000, PPT Vision, Inc., All Rights Reserved.
This invention is related to:
U.S. Pat. No. 6,603,103, entitled xe2x80x9cCIRCUIT FOR MACHINE-VISION SYSTEMxe2x80x9d,
U.S. patent application Ser. No. 09/350,050, entitled xe2x80x9cMACHINE-VISION SYSTEM AND METHOD FOR RANDOMLY LOCATED PARTSxe2x80x9d (now abandoned), filed Jul. 8, 1999,
U.S. patent application Ser. No. 09/350,255, entitled xe2x80x9cPARTS MANIPULATION AND INSPECTION SYSTEM AND METHODxe2x80x9d (now abandoned), filed Jul. 8, 1999,
U.S. patent application Ser. No. 09/349,684, entitled xe2x80x9cMACHINE-VISION SYSTEMS AND METHODS WITH UP AND DOWN LIGHTSxe2x80x9d (now abandoned), filed Jul. 8, 1999,
U.S. patent application Ser. No. 09/349,948, entitled xe2x80x9cMETHOD AND APPARATUS TO CALCULATE BGA BALL TOPSxe2x80x9d (now abandoned), filed Jul. 8, 1999,
U.S. Pat. No. 6,522,777, entitled xe2x80x9cCOMBINED 3D AND 2D-SCANNING MACHINE-VISION SYSTEM AND METHODxe2x80x9d
U.S. patent application Ser. No. 09/350,037, entitled xe2x80x9cMACHINE-VISION SYSTEM AND METHOD HAVING A SINE-WAVE PROJECTION PATTERNxe2x80x9d (now abandoned), filed Jul. 8, 1999,
U.S. patent application Ser. No. 09/350,251, entitled xe2x80x9cTRAY FLIPPER AND METHOD FOR PARTS INSPECTIONxe2x80x9d (filed Jul. 8, 1999,
U.S. Pat. No. 6,509,559, entitled xe2x80x9cBINARY GRATING AND METHOD FOR GENERATING A MOIRE PATTERN FOR 3D IMAGINGxe2x80x9d
U.S. Pat. No. 6,486,963, entitled xe2x80x9cPRECISION 3D SCANNER BASE AND METHOD FOR MEASURING MANUFACTURED PARTSxe2x80x9d
U.S. Pat. No. 6,501,554, entitled xe2x80x9c3D SCANNER AND METHOD FOR MEASURING HEIGHTS AND ANGLES OF MANUFACTURED PARTSxe2x80x9d
which are all assigned to a common assignee, and which are incorporated herein by reference.
There is a widespread need for inspection data for electronic parts in a manufacturing environment. Machine-vision systems have become vital to many complex manufacturing processes, particularly for quality control. For example, during the manufacture of integrated circuits which contain millions of transistors and other electrical components, machine-vision systems visually inspect the circuits at various manufacturing stages for surface blemishes or other defects, rejecting or accepting circuits based on appearance.
Machine-vision systems typically includes an imaging device, such as an electronic camera and an illumination system, which illuminates an object for the camera. The typical illumination system, generally designed to illuminate all sides of an object simultaneously, comprises some form of a circular ring of lights, for example a ring-shaped flashtube, a ring of light-emitting diodes, or a ring of optical fibers. The circular ring of lights usually lies between the camera and object, with the camera looking down through the ring to the object and the lights oriented down and inward to the object.
Conventional illumination systems suffer from at least two major problems. First, they lack a convenient way for varying the angle of illumination, that is, the angle light strikes an object. Conventional illumination systems require technicians to manually adjust orientation of the complete ring of lights or to manually adjust orientation of its individual lights. However, manual adjustments are not only time consuming, but often lead to angular variations which compromise consistency of machine-vision systems. Second, conventional systems lack convenient way of switching from one illumination mode to another, for example, from a particular selected angle of illumination to a multi-directional object illumination, such as xe2x80x9ccloudy-day illumination.xe2x80x9d Some select-angle illumination modes are better for viewing scratches, while cloudy-day illumination is better for specular or irregular surfaces. This lack of a convenient way of switching illumination modes often leads to use of more than one machine-vision system, and thus forces manufacturers to buy separate systems, to use human inspectors, or to skip inspection for some types of defects. Accordingly, there is a need for better illumination systems for machine-vision systems.
In the context of a machine-vision system for inspecting a part, this invention includes method and apparatus to provide high-speed changing and/or automatic adjustment of illumination angle, dispersion, intensity, and/or color of illumination in a machine vision system.
One aspect of the present invention provides a machine-vision system having an optical axis. This system includes a light source emitting light having a polarization, a machine-vision imager that obtains an image of an object illuminated by the light, a processor coupled to receive an image from the imager, and operative to generate a quality parameter based on the image, and one or more of the various means as described above for selectively directing the light in a predetermined pattern based on its polarization and based on the quality parameter of the image.
Another aspect of the present invention provides a machine-vision system having an optical axis. This system includes a machine-vision imager located along the optical axis, a controllable light source, a first optical element that selectively directs light in a first predetermined pattern relative to the optical axis based on light characteristics, a second optical element, that directs light in a second predetermined pattern relative to the optical axis, and an electronic controller operatively coupled to the imager and the controllable light source to control the light characteristics and thereby selecting one or more of the first and second predetermined patterns.
Another aspect of the present invention provides an illumination method that includes emitting light, selectively polarizing the light, and selectively directing the light based on its polarization.
In some embodiments, the selectively directing provides two or more different angles of illumination (e.g., alpha and/or beta). In some such embodiments, the angle is a conical angle of a ring illumination.
Yet another aspect of the present invention provides a machine-vision method for inspecting an object. This method includes (a) setting one or more illumination parameters, (b) illuminating the object based on the one or more illumination parameters, (c) obtaining an image of the illuminated object, (d) generating a quality parameter based on an image quality of a predetermined region of interest in the image, and (e) iterating (b), (c), and (d) using a different illumination parameter. In some embodiments of this method, the iterating is based on the quality parameter. In some embodiments, the one or more illumination parameters includes a predetermined azimuth angle of illumination. In some embodiments, the one or more illumination parameters includes a predetermined compass angle of illumination. In some embodiments, the one or more illumination parameters includes a predetermined compass angle of illumination.